Volume of a Rectangular Prism
A prism with bases that are all rectangles is called a Rectangular Prism. A cube is a special rectangular prism with all its faces congruent. Rectangular prisms are described by its dimensions: length, width, and height.

Volume is the number of cubic units it takes to fill a figure.
Watch the video, as a box (rectangular prism) is filled with linking cubes.
American Flag - Act 3 from Mr.Stadel on Vimeo.
How many linking cubes were used to fill the box (rectangular prism)?
How many cubes were used to represent the length of the box?
How many cubes were used to represent the width of the box?
Since you know the total number of the cubes in the box, how could you use this information to help you find the number of cubes it would take to represent the height of the box?